It is necessary to carry out the squeezing of the tubular fabric in an exactly defined manner during dyeing of the fabric with active dyes, in order to achieve a flawless product quality, that is to say, dyeing quality.
After squeezing by the generally known squeezing devices, wherein the tubular textile material strip is guided through two motorized squeezing rollers, one of which is rotatably mounted in a fixed position on the machine frame and the other of which is mounted to be adjustable relative to the first, two-ply flat tubular-fabric always has edge-markings. More specifically, the edge of the two-ply, flat tubular-fabric is deformed when squeezing rollers with relatively hard surfaces are used, while the squeezing effect is diminished if the rollers have a relatively soft surface. A portion of the refining solution that has been squeezed out of the tubular fabric, thereby flows along both sides of the two-ply, flat tubular-fabric back into the edge area of the fabric after the fabric has left the squeezing roller groove. This leads to qualitatively varying results in the removal of the refining solution across the width of the fabric. This means, for example, that in the center of the fabric the refining solution is almost completely removed, while undesired refining solution is still found in the edges, that is, in the bent edge. Thus, fabrics with a poor wettability have light edge-markings, while fabrics with a good wettability have darker markings.
Various efforts have been made to overcome the above problem which adversely affects the fabric quality. According to German Patent Publication (DE-OS) 3,619,922, a method of dyeing tubular fabrics and an apparatus to carry out the known method are described, which aim at reliably avoiding a permanent edge-marking even with hard to process materials and even when the recipe of the reaction dye is not optimally set.
It is shown in the DE-OS 3,619,922 that the edge-markings which form in the fabric during padding are displaced after said padding, and that after this displacement of the edge-markings, but before the cold dwelling time, the fabric is squeezed again. The apparatus to carry out the known method is only sketchily described. The construction of the apparatus for displacing the edge markings and for squeezing the tubular fabric is not described in detail.
German Patent Publication (DE-OS) 3,600,559 discloses an apparatus for wet processing continuously moving tubular fabric, which has for its aim the forming of the tubular fabric in such a way that all edge markings resulting from the squeezing out process are avoided and so that an especially uniform fabric output is achieved. To achieve this aim, it is suggested that a tubular spreader with a circular cross-section that reaches into the edge markings on both sides and spreads the fabric out, is provided along the right and left edges downstream of the squeezing rollers as viewed in the motion direction of the fabric. Each ring of the tubular spreader should thereby cooperate with a pressure roller lying on the outside, in such a way that the edge marking of the tubular fabric between the respective ring and pressure roller becomes equalized. However, this solution in the DE-OS 3,600,559 does not offer the possibility of generally avoiding edge markings altogether during wet processing of tubular fabric.
European Patent EP 0,166,316 describes a method for the removal of edge-markings in tubular knitted fabric and an apparatus for carrying out the method, whereby the edge-markings resulting from the squeezing-out effect during the dyeing of the tubular knitted fabric should be avoided altogether. According to European Patent EP 0,166,316 this is achieved in that the stitched fabric is inflated like a balloon by means of steam and then laid flat again at least once during the fixing of the applied dye. An apparatus to carry out the known method has at least one nozzle for inflating the stitched fabric, attached between the dipping trough and the guide rollers which guide the tubular fabric.